Changes in kinematics and arm–leg coordination during a 100-m breaststroke swim     

Samuel W. Oxford  Rob S. James  Michael J. Price  Carl J. Payton  Michael J. Duncan 《Journal of sports sciences》2017,35(16):1658-1665

The purpose of this study was to compare arm–leg coordination and kinematics during 100 m breaststroke in 26 (8 female; 18 male) specialist breaststroke swimmers. Laps were recorded using three 50-Hz underwater cameras. Heart rate and blood lactate were measured pre- and post-swim. Arm–leg coordination was defined using coordination phases describing continuity between recovery and propulsive phases of upper and lower limbs: coordination phase 1 (time between end of leg kick and start of the arm pull phases); and coordination phase 2 (time between end of arm pull and start of leg kick phases). Duration of stroke phases, coordination phases, swim velocity, stroke length (SL), stroke rate (SR) and stroke index (SI) were analysed during the last three strokes of each lap that were unaffected by turning or finishing. Significant changes in velocity, SI and SL (P < 0.05) were found between laps. Both sexes showed significant increase (P < 0.05) in heart rate and blood lactate pre- to post-swim. Males had significantly (P < 0.01) faster swim velocities resulting from longer SLs (P = 0.016) with no difference in SR (P = 0.064). Sex differences in kinematic parameters can be explained by anthropometric differences providing males with increased propelling efficiency.  相似文献   

Increasing hip and knee flexion during a drop-jump task reduces tibiofemoral shear and compressive forces: implications for ACL injury prevention training     

Liang-Ching Tsai  Yi-An Ko  Kyle E. Hammond  John W. Xerogeanes  Gordon L. Warren  Christopher M. Powers 《Journal of sports sciences》2017,35(24):2405-2411

Although most ACL injury prevention programmes encourage greater hip and knee flexion during landing, it remains unknown how this technique influences tibiofemoral joint forces. We examined whether a landing strategy utilising greater hip and knee flexion decreases tibiofemoral anterior shear and compression. Twelve healthy women (25.9 ± 3.5 years) performed a drop-jump task before and after a training session (10–15 min) that emphasised greater hip and knee flexion. Peak tibiofemoral anterior shear and compressive forces were calculated using an electromyography (EMG)-driven knee model that incorporated joint kinematics, EMG and participant-specific muscle volumes and patella tendon orientation measured using magnetic resonance imaging (MRI). Participants demonstrated a decrease in peak anterior tibial shear forces (11.1 ± 3.3 vs. 9.6 ± 2.7 N · kg^?1; P = 0.008) and peak tibiofemoral compressive forces (68.4 ± 7.6 vs. 62.0 ± 5.5 N · kg^?1; P = 0.015) post-training. The decreased peak anterior tibial shear was accompanied by a decrease in the quadriceps anterior shear force, while the decreased peak compressive force was accompanied by decreased ground reaction force and hamstring forces. Our data provide justification for injury prevention programmes that encourage greater hip and knee flexion during landing to reduce tibiofemoral joint loading.  相似文献   

Email: An Appraisal Approach     

Daniel W. Noonan 《Journal Of Archival Organization》2016,13(3-4):146-151

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Educational leadership and pupil achievement in primary education     

W. van de Grift  A.A.M. Houtveen 《School Effectiveness & School Improvement》2013,24(4):373-389

Educational leadership can be defined as the ability of a principal to initiate school improvement, to create a learning-oriented educational climate, and to stimulate and supervise teachers in such a way that the latter may execute their tasks as effectively as possible. In 1989, 1993, and 1998, teacher perceptions of educational leadership of principals in Dutch elementary education were evaluated by means of a Rasch-scale. It turned out that the educational leadership of Dutch principals has grown considerably. In both 1989 and 1993 the effect of educational leadership on pupil achievement was investigated. While in 1989 no significant relationship was found, the results of 1993 show a significant relationship between educational leadership and average pupil achievement over 3 successive years corrected for school environment.  相似文献   

Implications for improving access and outcomes for individuals with disabilities in postsecondary distance education     

Weol Soon Kim‐Rupnow  Peter W. Dowrick  Laure S. Burke 《The American journal of distance education》2013,27(1):25-40

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(6) Commercial libraries     

C. W. Black 《International Information and Library Review》2013,45(4):485-492

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Knowing and teaching science: the constructivist paradox     

W. Louden  J. Wallace 《International Journal of Science Education》2013,35(6):649-657

This paper addresses the parallel between the changes in students' and teachers' learning advocated by constructivist science educators. It begins with a summary of the epistemology of constructivism and uses a vignette drawn from a set of case studies to explore the impact of a constructivist science in‐service programme on an experienced and formal elementary science teacher. Judged by constructivist standards, the teacher described in the vignette makes very little progress. The irony of applying a constructivist critique to his work, however, is that it fails to treat the teachers' imperfect knowledge of teaching with the same respect as constructivists treat students' imperfect learning of science. The remainder of the paper explores this constructivist paradox, and suggests that‐like students' knowledge of science‐teachers' knowledge of constructivist science teaching is likely to grow through slow and gradual re‐formation of their established understanding of classroom theory and practice.  相似文献   

Television: The performance of nonresident students in the “economics U$A” telecourse     

Paul W. Grimes  Joyce E. Nielsen  James F. Niss 《The American journal of distance education》2013,27(2):36-43

Abstract

Correspondence study represents the first and most persistent distance education format in American universities. Later called independent study, it enabled universities to disseminate instruction far beyond their campuses. Yet, national‐level leadership provided by the National University Continuing Education Association (NUEA) and its divisions has been relatively restrained. In contrast, leadership in the private correspondence school sector has been assertive, and sometimes even aggressive. The NUEA and its members shunned this approach, choosing instead to lead by persuasion and example. The NUEA developed standards of practice concerned primarily with replicating on‐campus teaching styles and values, rather than the promotion of distance education. With the abolition of its division structure, the NUEA's successor, the University Continuing Education Association (UCEA), has opted out of a leadership role in independent study. This paper concludes that the NUEA's initial attempt at leadership in distance education— while reasoned and principled—contained flaws that made failure inevitable.  相似文献   

Teacher perceptions of students' self‐concepts     

Mary W. Lasseigne 《The Teacher Educator》2013,48(3):38-40

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Toward a cultural critique of Victorian periodicals     

Mark W. Turner 《Media History》2013,19(1-2):111-125

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